In the 1971 semifinal against the Black Hawks, "Stemmer" or "Stem" scored the game winner in Game 1 after just 1:37 of overtime. The Rangers would lose Game 5 in overtime, only to be in the same position in Game 6. Facing elimination, the Rangers forced a deciding seventh game when Stemkowski scored at 1:29 of the third overtime – a total of 41:29 of extra time. The MSG Network special The 50 Greatest Moments in Madison Square Garden History placed the Game 6 triple overtime winner at number 18.
He has served a stint as the television (1992–1996) and radio color commentator (2000–2005) for the San Jose Sharks and now does so for the New York Rangers on a part-time basis. He was rumoured to be a candidate to become the Rangers' full-time radio analyst in 2006–07 but has retained his back-up role and makes appearances at Rangers events.
On May 7, 1982, Stemkowski pleaded guilty to a single misdemeanor count of criminal solicitation in Nassau County, New York. Stemkowski had lent $35,000 to a business associate, which had not been repaid along with $35,000 in interest. He offered $20,000 to an undercover Nassau County police officer to fly to California and break an ankle and wrist of the business associate. By pleading guilty, Stemkowski avoided a charge of conspiracy.